While such engines use “diesel” as a fuel, such fuel can be usefully supplemented by other fuels in certain circumstances.
This invention relates to a fuel supplementation process and method and to an arrangement for using supplementary fuels in engines of this type.
Characteristics of this type of engine include a main fuel injection system, means to change an amount of main fuel being injected into the engine in response to load demands on the engine, and an air supply. This type of engine works best with an approximately constant pressure cycle which provides a relatively flat torque curve and generally low specific fuel consumption. However this ideal is not readily achieved. One factor in this is that in order to achieve a reliable and instant ignition requires a fuel with a high cetane rating but in order to then achieve a long slow burn requires a fuel with a low cetane rating. To achieve reliable ignition with a subsequent long slow burn then essentially requires two different fuels. This is where fuel supplementation can be very advantageous where a main fuel is a fuel with a high cetane rating and the subsequent supplementary fuel is a fuel which is high octane and low cetane rating.
It is currently known to provide some fuel supplementation by adding supplementary fuel into an air supply where a “diesel” or compression ignition engine is turbo charged.
However, one of the difficulties that currently exists is the difficulty of ensuring that there is an appropriate ratio of supplementary fuel and air through changing load conditions.